Contact bank



. Aug. 11, 1936.

FIG. 2.

Filed March 7, 1934 Patented Aug. 11, 1936 UNITED STATES PATENT OFFICE 2,050,419 oom'ac'r BANK Application March 7, 1934, Serial No. 714,436

4 Claims.

This invention relates to contact banks, and with-regard to certain more specific features, to contact banks for successively cutting in and cutting out sections of a resistance, bank.

This invention is an improvement upon'the structure disclosed in my United States Patent 1,982,461 for Electric governor, dated November 27, 1934. i

Among the several objects of the invention may be noted the provision of apparatus of the class described wherein the last contact is as free from pitting, corrosion and smudging as any of the others therein; the provision of apparatus of this classin which mutual wiping of all contacts is effective after they are all closed; and the provision of apparatus of the class described which is relatively simple in construction and operation. Otherobjects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of partswhich will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which are illustrated several of various possible embodiments of the invention,

Fig. 1 is a fragmentary side elevation showing a single row of separated contacts;

Fig. 2 is a view similar to Fig. 1 but reduced in scale and showing thecontacts forced together;

Fig. 3 is a diagrammatic assembly; and,

Fig. 4 is a' view similar to Fig. 1 showing another form of the invention.

Similar reference characters indicate corresponding parts throughout the several views of ing-resistance into a circuit IS. The circuit I5 is a circuit by. means of which a battery I1 is caused to energize the field windings I9 on the u electro-magnetic armature l5.v

, rosion and smudging.

cordingly as the speed increased, thereby throw- In the present invention it is desired to improve the operation of banks of contacts.

Such large resistance values are required in the electric governors for air conditioning that it is found necessary to .thus put contacts in 5 multiple series rows and still operate them from a common lever, and the present invention applies both to single and multiple series rows. Getting both rows to positively close when using a fixed stop has developed into 'a serious service 10 problem. Certain contact leaves also did not get sufiicient contact pressure when wiping action occurred. Hence they were not self-cleaning resulting in ineflicient contacting with pitting, cor- 15 Referring specifically to Fig. 3, it will be seen that one contact roller 25 is used but more may be used if more contact series are desired. One of these rollers 25 is shown in Figure 1 opposite a row of button contacts 21 which are located on go flexible leaf springs 29, the latter being mounted on an arbor 3| but insulated from one another. The leaf springs 29 are adapted to be bent as shown in Figure 2 when the pressure roller 25 advances to the left. In so bending they suc- 25 cessively contact from right to left with the contact pressure between pairs increasing as the number of contacts increases, and vice versa. Thus as the roller 25 proceeds to the right under increased speeds, the contacts successively open 30 to the right and successively cut in resistance units.

Opposite the last leaf spring 29 and contact 21 is slidably mounted a preloading stop 33, said stop 33 acting resiliently against a spring 35, the 35 latter abutting a cotter key 31. The cotter key 31 intersects an opening 39 in a fixed stop-screw 4|. As shown in the drawing, said spring 35 is within said opening39.

The stop-screw 4! is threaded for adjustment through an arm 43 and adapted to be locked in any adjusted position by means of a lock nut 45.

A seal 41 acts as a further lock and indicator of any tampering with the apparatus. 11; n be seen from the above that as the pressure roller advances to the left, the successive leaf springs or blades-are bent to the left, thereby successively contacting the button head con- "tacts 21 and thereby shorting out whatever resistance may be placed across successive contacts.

The action is ideal because there is substantially right angular movement of the contact surfaces iuntil contact is attained, after which a lateral wiping action maintains the contacts bright and efllclent. At the same time the increasing pressure between contact surfaces, as the leaf springs are bent, provides a very smooth cutting out-of the resistances. It will be understood that the resistance at a given pair of contacts is reduced in a proportion to the pressure increase at the contacts.

As the last contact il is contacted by the second-to-last contact 21, it is in turn pushed to the left and forces the resiliently mounted resistance stop 33 to the left. This action permits wiping between the last two contacts in the same manner that the other contacts wipe and permits of further wiping of all contacts after all are closed. However, it is not proper to permit this action to proceed indefinitely and it does not do so, for the last contact finally strikes the fixed surface 49 on the adjustable fixed stop 4|.

The movement 01 the plunger or plug 33 is of the order of one-sixteenth of an inch which aiiords proper-wiping action. This portion of the invention may be characterized as the provision of a series of spring mounted contacts, the

last one of which engages a pre-loaded plunger stop having a definitely limited movementv to prevent excess deflection oi the spring mountings for said contacts. By this means is obtained the controlled pressure wiping action. This also provides a preloaded range of movement for the roller 25 toward the right under incr conditions. During this range of movement no resistance is cut in as no contacts open and the apparatus may gain a certain minimum speed without hunting over the range.

It will be seen from the above that the preloaded plunger 33 effects an equalizing feature, so that it adjustment of the pressure roller 25 is inaccurate, the plunger 33 will permit proper complete engagement.

Thus, by means of this invention, not only is the action of a single row of contacts improved, but provision is made for increasing the capacity of this type of resistance by permitting two'banks oi the sameto be successfully operated simultaneously, if desired.

It will be understood that in Fig. 3, the showing of one row of three contacts and two resistances is suggestive only, and that as many contact banks may be used as may-be desirable in a given design.

As shown in Figure 4,'the invention may be carried out by Providing a series of leaf springs 2a of which the last so, is made stronger than the remainder. The sliding plug 33 is omitted but the fixed stop 4| being retained at a predetermined distance ironi the last, relatively strong spring 30. By this means, bending oi the last contact is efiected for predetermined distance and thus wiping is eflected, but the desired predetermined'final stop is had. In either the Fig. 1

1 or the Fig. 4 form, the action at the last contact has the efi'ect oi preloading the contacts in the gspeed means, a positive stop adapted to limit the motion rind of time, that is, all contact opening is delayed until the last, preloading contact traverses its path of movement from the fixed stop surface 49. The provision of this movement also permits i'ull wiping contact at all contact points and the successtul operation of a plurality of contact banks from a single source of movement. The movement being adjustable permits adjustment of the degree of preloadingso that the apparatus may readily be set to operate at best efilciency under 10 any of varying outside conditions.

In view of the above, it will be seen that the several objects of the invention areachieved and other advantageous results attained.

As many changes could be made in carryin 15 out the above constructions without departing from the scope or the invention, it is intended that all matter contained in the'above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim: N 1. In electrical shunting apparatus having a series of movably mounted shunting contacts and pressure means operable from one end against 25 the series to successively close and open the same, means supporting the last contact at the other end of the series effecting a higher resistance to movement than is eflected in connection with the other contacts, and an adjustable fixed stop for adjustably determining the maximum fixed stop for determining the amount of said movement when all contacts are closed.

3. In electrical shunting apparatus having a series of movable spring-mounted contacts and movable pressure means operable from one end of the series, an adjustable fixed stop at the other end or the series, a movable stop supported by said fixed stop and adapted to be' engaged by the last contact of said series, and resilient means reacting between the-fixed stop and the movable stop. 4. In electrical shunting apparatus having a series of movable spring-mounted contacts and movable pressure means operable from one end of the series, a movable stop engaging the opposite end contact 01' the series, resilient means coop'ei ating with said movable stop providing substant a1 pre-loading between all contacts after they have closed to maintain a complete closure for a predetermined part of the movement of the pressure of all contacts while closed and means for adjusting said positive stop so that the limited motion and amount of pre-loading may be predetermined.

ANTHONY wm'mnn. 

